Research on valve internal leakage monitoring based on single acoustic sensor

doi:10.11949/j.issn.0438-1157.20190007

Abstract

Abstract:

Aiming at simulation and monitoring for valve internal leakage, a single-senor based non-intrusive acoustic monitoring method for valve internal leakage and a valve internal leakage simulation method are proposed. A virtual valve composed of a flange, thin paper sheet and perforated aluminum sheet is designed, which can truly simulate the transient leakage of a valve and overcome shortcomings in traditional valve internal leakage simulation method. By analyzing and comparing the frequency domain characteristics of the output signal of the upstream and downstream acoustic sensors under different conditions, the redundancy of the upstream acoustic sensor and the feasibility of single-sensor based acoustic monitoring method for valve internal leakage are verified. The time-frequency domain characteristics of the output signal of single acoustic sensor under different conditions are analyzed and compared, a time-frequency domain feature extraction method for acoustic signals based on wavelet packet energy fractionation and the kurtosis coefficient is proposed, the valve internal leakage diagnosis model based on support vector data description method (SVDD) was established with the normal samples under valve closed condition. The experimental results show that the proposed method for valve internal leakage monitoring with single acoustic sensor is effective, and it has strong anti-interference ability and high detection sensitivity.

Key words: valve internal leakage, non-intrusive, single-sensor structure, acoustic monitoring, virtual valve

摘要：

针对阀门内漏模拟和阀门内漏监测问题，提出了阀门内漏模拟和阀门内漏非介入式单声波传感器监测方法。设计了由法兰、薄纸片和带孔铝片组成的虚拟阀门，可真实地模拟阀门内漏瞬态过程，克服了传统阀门内漏模拟方法中存在的各种缺点。分析、比较了不同条件下阀门上下游声波传感器输出信号的频域特征，验证了阀门上游声波传感器设置的冗余性和基于单声波传感器实现阀门内漏监测的可行性。分析、比较了不同条件下单声波传感器输出信号的时频域特征，提出了基于峰值系数和小波包能量分率的阀门内漏时频域特征提取方法，并以阀门密封良好状态下的声波信号为样本，建立了基于SVDD的阀门内漏诊断模型。测试结果表明：本文提出的单声波传感器阀门内漏监测方法可行、模型诊断准确，且具有较强的抗干扰能力和较高的阀门内漏检测灵敏度。

关键词: 阀门内漏, 非介入式, 单传感器, 声波监测, 虚拟阀门

CLC Number:

TE 988

Wenliang WANG, Fang WANG, Shi en WU, Weiguo LIN. Research on valve internal leakage monitoring based on single acoustic sensor[J]. CIESC Journal, 2019, 70(S1): 248-256.

王文亮, 王芳, 吴石恩, 林伟国. 阀门内漏单声波传感器监测方法研究[J]. 化工学报, 2019, 70(S1): 248-256.

Figures/Tables 19

Fig.1 Experimental platform of valve internal leakage monitoring system

Fig.2 Internal structure of virtual valve

Fig.3 Comparison of frequency domain characteristics of upstream and downstream acoustic signals under valve normal condition

Fig.4 Comparison of frequency domain characteristics of upstream and downstream acoustic signals under valve internal leakage

Fig.5 Comparison of frequency domain characteristics of upstream and downstream acoustic signals under pump starting condition

Fig.6 Downstream acoustic signals under valve normal and internal leakage conditions

Table 1 Test condition

参数名称	数值
阀门上游压力	200 kPa
阀门下游压力	101 kPa
阀门泄漏孔径	1.7%阀门开度
管道直径	DN20
管壁厚度	6 mm
信号采样频率fs	100 Hz

Fig.7 Probability density curves of downstream acoustic signals under valve normal and internal leakage conditions

Table 2 Acoustic signal time domain characteristic parameters

序号	均方根值（RMS）/mV	峰度系数（K_u）
1	36.3598	3.3304
2	37.0721	3.4176
3	36.4608	3.3501
4	36.8929	3.3946
5	36.3821	3.2689
6	124.4467	7.1149
7	118.4837	11.1468
8	125.7384	9.5663
9	116.4211	8.3873
10	131.8745	9.9753

Fig.8 Values of RMS and kurtosis coefficient of acoustic signal under different pipeline pressure conditions

Fig.9 Power spectrum of acoustic signal under valve normal and internal leakage conditions

Table 3 Power spectrum gravity under valve normal and internal leakage conditions/Hz

序号	阀门正常	瞬态内漏
1	16.4332	5.7205
2	16.7183	8.5889
3	16.7863	3.9855
4	16.6846	5.8735
5	16.454	6.7332
6	16.7299	4.1248
7	17.3117	6.4734
8	16.4612	4.2227
9	17.479	7.0074
10	17.2883	4.2243
均值	16.8347	5.6954

Fig.10 Wavelet packet energy rate of acoustic signal under valve normal and internal leakage conditions

Fig.11 First type of error and radius of hypersphere vary with kernel parameter σ

Table 4 Test sample set

管道压力/kPa	正常样本帧数	内漏样本帧数
100	90	5
200	70	10
300	85	5

Fig.12 Results of SVDD model test

Fig.13 Start-stop pump test

Fig.14 Results of environmental noise test

Table 5 Test results of sensitivity test

泄漏孔径/mm	阀门上游压力/kPa	平均泄漏量/（L/min）	模型输出f(z) （第1/2次）
0.8	210	0.328	0.0234/0.0216
1	240	0.540	0.0426/0.0666
2	220	1.933	0.8905/0.6025
3	200	4.375	0.5896/0.9449

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